Gas generant compositions

ABSTRACT

A novel composition, used for example, as an autoignition and/or booster composition  12 , contains cellulose acetate butyrate, nitroguanidine, a metal perchlorate such as potassium perchlorate, a first additive that liberates molybdenum trioxide during combustion, and a second additive selected from well known fuels used in gas generating systems. The novel composition is contained for example within a gas generator  10 . The gas generator  10  may be contained within a gas generating system such as an airbag inflator  10  or seat belt assembly  150 , or more broadly within a vehicle occupant protection system  200.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 60/875,300 filed on Dec. 15, 2006.

TECHNICAL FIELD

The present invention relates generally to gas generating systems, andto autoignition and booster compositions employed in gas generatordevices for automotive restraint systems, for example.

BACKGROUND OF THE INVENTION

The present invention relates to autoignition compositions that uponignition provide the flame front and pressure front necessary to safelyignite gas generant compositions in combustible communication therewith.As known in the art, gas generators are typically provided with anautoignition composition that in the event of a fire ignites responsiveto a desired threshold temperature. As a result, the gas generant isignited prior to melting for example, thereby safely igniting the maingas generant composition to inhibit or prevent the likelihood of anexplosive event once the gas generant begins to combust.

An ongoing challenge is to simplify the manufacture of a gas generatorby reducing the constituents required in the production thereof. Forexample, in many gas generators used in vehicle occupant protectionsystems, several discrete compositions are provided to servecorrespondingly discrete functions. These compositions often include aprimary gas generating composition that when combusted is employed toprovide sufficient quantities of gaseous products to operate theassociated restraint device, such as an airbag or seatbelt pretensioner.A booster composition is utilized to elevate the pressure and heatwithin the gas generator prior to combustion of the primary gasgenerant, thereby creating favorable conditions within the inflator foracceptable combustion of the primary gas generant. Of course, still yetanother composition is the auto-ignition composition employed to providesafe combustion of the other compositions in the event of a fire. Theauto-ignition composition is designed to ignite at temperatures belowthe melting point of the primary gas generant for example, therebyensuring the controlled combustion of the primary gas generant, asopposed to an explosive reaction perhaps.

The use of compositions containing cellulose acetate butyrate (CAB),nitroguanidine (NQ), and potassium perchlorate (KP) as gas generantcompositions is known. These compositions provide relatively largeamounts of gas and relatively small amounts of solids upon combustion.However, the ignition temperature is over 500 degrees Celsius. Seatbeltpretensioners utilizing this composition disassemble when subjected toDOT and BAM rapid heating tests. Even so, this composition is desirablegiven the relatively cheap costs and also because of the large amountsof gas produced. It would therefore be an improvement in the art tostabilize the ignition and combustion of a CAB composition to make ituseful in smaller micro gas generators used in seatbelt devices, forexample.

SUMMARY OF THE INVENTION

The above-referenced concerns and others may be resolved by gasgenerating systems including an autoignition/booster compositioncontaining a first oxidizer selected from metal perchlorates, such aspotassium perchlorate, at about 10-90 weight percent of the composition,and a fuel component of CAB and NQ that when taken together are providedat about 10-90 weight percent of the composition. In accordance with thepresent invention, a first additive of molybdenum trioxide is providedat about 0.1-3 wt % of the total composition. Alternatively, anycompound that would liberate molybdenum trioxide in the same relativemolar/weight amounts during combustion may also be provided as the firstadditive. These include molybdic acid, ammonium molybdate, sodiummolybdate, phosphomolybdic acid, ammonium phosphomolybdate, and sodiumphosphomolybdate. A second additive of 5-aminotetrazole is provided atabout 0.1-5 wt % of the total composition. Alternatively, anyazole-based fuel including metal salts of azole compounds, and azolecompounds such as aminotetrazole, tetrazole, 5-nitrotetrazole,5-nitroaminotetrazole, and bitetrazole, may be included in the sameweight percent range, or, in the same molar-effective amounts.Alternatively, triazole-based compounds including 1,2,4-triazole-5-oneor 3-nitro-1,2,4-triazole-5-one and metal salts of these compounds mayalso be employed either singularly or in conjunction with thetetrazole-based compounds in the same weight percent range, or in thesame molar-effective amounts. Alternatively, guanidine nitrate,aminoguanidine nitrate, triaminoguanidine nitrate, nitroguanidine,dicyandiamide, triazalone, nitrotriazalone, and mixtures thereof mayalso be employed either singularly or in conjunction withtetrazole-based and/or triazole-based compounds in the same weightpercent range of about 0.1-5 weight percent when taken as a whole, or inthe same molar-effective amounts as the azole-based second additive.

In further accordance with the present invention, a gas generator and avehicle occupant protection system incorporating the autoignition systemare also included. A seat belt device as known in the art may alsocontain a composition as described above may also be included.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view showing the general structure ofan inflator in accordance with the present invention.

FIG. 2 is a schematic representation of an exemplary vehicle occupantrestraint system containing a gas generant composition in accordancewith the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A primary fuel component is provided containing cellulose acetatebutyrate (CAB) and nitroguanidine (NQ). The primary fuel component isprovided at about 10-90 wt % of the gas generant composition. Each fuelconstituent of the primary fuel component may generally be provided atabout 5-95 wt % relative to the weight of the primary fuel component. Afirst additive selected from molybdenum trioxide, molybdic acid,ammonium molybdate, sodium molybdate, phosphomolybdic acid, ammoniumphosphomolybdate, and sodium phosphomolybdate, is provided at about0.1-3 weight percent (wt %). Stated another way, any component thatwould liberate molybdenum trioxide in the same relative molar amountsmay also be provided.

A second additive is selected from one or more secondary fuels includingtetrazoles such as 5-aminotetrazole; metal salts of azoles such aspotassium 5-aminotetrazole; nonmetal salts of azoles such as diammoniumsalt of 5,5′-bis-1H-tetrazole; nitrate salts of azoles such as5-aminotetrazole; nitramine derivatives of azoles such as5-aminotetrazole; metal salts of nitramine derivatives of azoles such asdipotassium 5-aminotetrazole; metal salts of nitramine derivatives ofazoles such as dipotassium 5-aminotetrazole; nonmetal salts of nitraminederivatives of azoles such as monoammonium 5-aminotetrazole;triazole-based compounds including 1,2,4-triazole-5-one or 3-nitro-1,2,4triazole-5-one and metal salts of these compounds; guanidines such asdicyandiamide; salts of guanidines such as guanidine nitrate; nitroderivatives of guanidines such as nitroguanidine; azoamides such asazodicarbonamide; nitrate salts of azoamides such as azodicarbonamidinedinitrate; and mixtures thereof. The secondary fuel can be used withinthis system as co-fuels to the primary fuel. The second additiveconstitutes about 0.1-5 wt %.

An oxidizer component is selected from metal perchlorates, such aspotassium perchlorate at about 10-90 wt % of the composition.

The compositions of the present invention are formed from constituentsas provided by known suppliers such as Aldrich or Fisher Chemicalcompanies. The compositions may be provided in granulated form anddry-mixed and compacted in a known manner, or otherwise mixed as knownin the art. The compositions may be employed in gas generators typicallyfound in airbag devices or occupant protection systems, or in safetybelt devices, or in gas generating systems such as a vehicle occupantprotection system, all manufactured as known in the art, or asappreciated by one of ordinary skill.

As shown in FIG. 1, an exemplary inflator or gas generating system 10incorporates a dual chamber design to tailor containing anautoignition/booster composition 12 formed as described herein, may bemanufactured as known in the art. U.S. Pat. Nos. 6,422,601, 6,805,377,6,659,500, 6,749,219, and 6,752,421 exemplify typical airbag inflatordesigns and are each incorporated herein by reference in their entirety.

Referring now to FIG. 2, the exemplary inflator or gas generating system10 described above may also be incorporated into an airbag system orvehicle occupant protection system 200. Airbag system 200 includes atleast one airbag 202 and an inflator 10 containing a gas generantcomposition 12 in accordance with the present invention, coupled toairbag 202 so as to enable fluid communication with an interior of theairbag. Airbag system 200 may also include (or be in communication with)a crash event sensor 210. Crash event sensor 210 includes a known crashsensor algorithm that signals actuation of airbag system 200 via, forexample, activation of airbag inflator 10 in the event of a collision.

Referring again to FIG. 2, airbag system 200 may also be incorporatedinto a broader, more comprehensive vehicle occupant restraint system 180including additional elements such as a safety belt assembly 150. FIG. 2shows a schematic diagram of one exemplary embodiment of such arestraint system. Safety belt assembly 150 includes a safety belthousing 152 and a safety belt 100 extending from housing 152. A safetybelt retractor mechanism 154 (for example, a spring-loaded mechanism)may be coupled to an end portion of the belt. In addition, a safety beltpretensioner 156 containing gas generating/auto ignition composition 12may be coupled to belt retractor mechanism 154 to actuate the retractormechanism in the event of a collision. Typical seat belt retractormechanisms which may be used in conjunction with the safety beltembodiments of the present invention are described in U.S. Pat. Nos.5,743,480, 5,553,803, 5,667,161, 5,451,008, 4,558,832 and 4,597,546,incorporated herein by reference. Illustrative examples of typicalpretensioners with which the safety belt embodiments of the presentinvention may be combined are described in U.S. Pat. Nos. 6,505,790 and6,419,177, incorporated herein by reference.

Safety belt assembly 150 may also include (or be in communication with)a crash event sensor 158 (for example, an inertia sensor or anaccelerometer) including a known crash sensor algorithm that signalsactuation of belt pretensioner 156 via, for example, activation of apyrotechnic igniter (not shown) incorporated into the pretensioner. U.S.Pat. Nos. 6,505,790 and 6,419,177, previously incorporated herein byreference, provide illustrative examples of pretensioners actuated insuch a manner.

It should be appreciated that safety belt assembly 150, airbag system200, and more broadly, vehicle occupant protection system 180 exemplifybut do not limit vehicle occupant protection systems contemplated inaccordance with the present invention.

It should further be understood that the preceding is merely a detaileddescription of various embodiments of this invention and that numerouschanges to the disclosed embodiments can be made in accordance with thedisclosure herein without departing from the scope of the invention. Thepreceding description, therefore, is not meant to limit the scope of theinvention. Rather, the scope of the invention is to be determined onlyby the appended claims and their equivalents.

1. A composition comprising: a first fuel containing cellulose acetatebutyrate and nitroguanidine, said first fuel provided at about 10-90weight percent of the total composition; an oxidizer containing one ormore metal perchlorates provided at about 10-90 weight percent of thetotal composition; a first additive containing at least one constituentselected from molybdenum trioxide, molybdic acid, ammonium molybdate,sodium molybdate, phosphomolybdic acid, ammonium phosphomolybdate, andsodium phosphomolybdate, is provided at about 0.1-3 weight percent ofthe total composition; a second additive containing at least oneadditive selected from tetrazoles such as 5-aminotetrazole; metal saltsof azoles such as potassium 5-aminotetrazole; nonmetal salts of azolessuch as diammonium salt of 5,5′-bis-1H-tetrazole: nitrate salts ofazoles such as 5-aminotetrazole; nitramine derivatives of azoles such as5-aminotetrazole; metal salts of nitramine derivatives of azoles such asdipotassium 5-aminotetrazole; metal salts of nitramine derivatives ofazoles such as dipotassium 5-aminotetrazole; nonmetal salts of nitraminederivatives of azoles such as monoammonium 5-aminotetrazole;triazole-based compounds including 1,2,4-triazole-5-one or 3-nitro-1,2,4triazole-5-one and metal salts of these compounds; guanidiness such asdicyandiamide; salts of guanidines such as guanidine nitrate; nitroderivatives of guanidines such as nitroguanidine; azoamides such asazodicarbonamide; nitrate salts of azoamides such as azodicarbonamidinedinitrate; and mixtures thereof, said second additive provided at about0.1-5 weight percent of the total composition.
 2. A gas generatingsystem containing the composition of claim
 1. 3. A vehicle occupantprotection system containing the composition of
 1. 4. The composition ofclaim 1 wherein said metal perchlorate is potassium perchlorate.
 5. Thecomposition of claim 1 containing cellulose acetate butyrate andnitroguanidine that when taken together are provided at about 10-90weight percent, potassium perchlorate at about 10-90 weight percent,molybdenum trioxide at about 0.1-3 weight percent, and 5-aminotetrazoleat about 0.1-5 weight percent, said percentages relative to the totalweight of the composition.
 6. The composition of claim 1 where thecellulose acetate butyrate and the nitroguanidine are each provided atabout 5-95 wt % of the weight of the first fuel.
 7. A compositioncomprising: a first fuel containing cellulose acetate butyrate andnitroguanidine; an oxidizer containing one or more metal perchlorates; afirst additive containing at least one constituent selected frommolybdenum trioxide, molybdic acid, ammonium molybdate, sodiummolybdate, phosphomolybdic acid, ammonium phosphomolybdate, and sodiumphosphomolybdate; and a second additive containing at least one additiveselected from a secondary fuel.
 8. The composition of claim 7 containingpotassium perchlorate.
 9. The composition of claim 7 wherein said firstfuel is provided at about 10-90 weight percent, said oxidizer isprovided at about 10-90 weight percent, said first additive is providedat about 0.1 to 3 weight percent, and said second additive is providedat about 0.1-5 weight percent, said weight percentages stated relativeto the total weight of the composition.
 10. The composition of claim 7wherein said second additive is selected from the group consisting oftetrazoles such as 5-aminotetrazole; metal salts of azoles such aspotassium 5-aminotetrazole; nonmetal salts of azoles such as diammoniumsalt of 5,5′-bis-1H-tetrazole: nitrate salts of azoles such as5-aminotetrazole; nitramine derivatives of azoles such as5-aminotetrazole; metal salts of nitramine derivatives of azoles such asdipotassium 5-aminotetrazole; metal salts of nitramine derivatives ofazoles such as dipotassium 5-aminotetrazole; nonmetal salts of nitraminederivatives of azoles such as monoammonium 5-aminotetrazole;triazole-based compounds including 1,2,4-triazole-5-one or 3-nitro-1,2,4triazole-5-one and metal salts of these compounds; guanidiness such asdicyandiamide; salts of guanidines such as guanidine nitrate; nitroderivatives of guanidines such as nitroguanidine; azoamides such asazodicarbonamide; nitrate salts of azoamides such as azodicarbonamidinedinitrate; and mixtures thereof.
 11. A composition comprising: a firstfuel containing cellulose acetate butyrate and nitroguanidine; anoxidizer containing one or more metal perchlorates; a first additivecontaining a compound that liberates molybdenum trioxide duringcombustion; and a second additive containing at least one additiveselected from a secondary fuel.